1 //===-- CodeGen/MachineFrameInfo.h - Abstract Stack Frame Rep. --*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // The file defines the MachineFrameInfo class.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_CODEGEN_MACHINEFRAMEINFO_H
15 #define LLVM_CODEGEN_MACHINEFRAMEINFO_H
17 #include "llvm/ADT/BitVector.h"
18 #include "llvm/ADT/DenseMap.h"
19 #include "llvm/ADT/SmallVector.h"
20 #include "llvm/System/DataTypes.h"
28 class TargetRegisterClass;
30 class MachineModuleInfo;
31 class MachineFunction;
32 class MachineBasicBlock;
33 class TargetFrameInfo;
35 /// The CalleeSavedInfo class tracks the information need to locate where a
36 /// callee saved register in the current frame.
37 class CalleeSavedInfo {
41 const TargetRegisterClass *RegClass;
45 CalleeSavedInfo(unsigned R, const TargetRegisterClass *RC, int FI = 0)
52 unsigned getReg() const { return Reg; }
53 const TargetRegisterClass *getRegClass() const { return RegClass; }
54 int getFrameIdx() const { return FrameIdx; }
55 void setFrameIdx(int FI) { FrameIdx = FI; }
58 /// The MachineFrameInfo class represents an abstract stack frame until
59 /// prolog/epilog code is inserted. This class is key to allowing stack frame
60 /// representation optimizations, such as frame pointer elimination. It also
61 /// allows more mundane (but still important) optimizations, such as reordering
62 /// of abstract objects on the stack frame.
64 /// To support this, the class assigns unique integer identifiers to stack
65 /// objects requested clients. These identifiers are negative integers for
66 /// fixed stack objects (such as arguments passed on the stack) or nonnegative
67 /// for objects that may be reordered. Instructions which refer to stack
68 /// objects use a special MO_FrameIndex operand to represent these frame
71 /// Because this class keeps track of all references to the stack frame, it
72 /// knows when a variable sized object is allocated on the stack. This is the
73 /// sole condition which prevents frame pointer elimination, which is an
74 /// important optimization on register-poor architectures. Because original
75 /// variable sized alloca's in the source program are the only source of
76 /// variable sized stack objects, it is safe to decide whether there will be
77 /// any variable sized objects before all stack objects are known (for
78 /// example, register allocator spill code never needs variable sized
81 /// When prolog/epilog code emission is performed, the final stack frame is
82 /// built and the machine instructions are modified to refer to the actual
83 /// stack offsets of the object, eliminating all MO_FrameIndex operands from
86 /// @brief Abstract Stack Frame Information
87 class MachineFrameInfo {
89 // StackObject - Represent a single object allocated on the stack.
91 // SPOffset - The offset of this object from the stack pointer on entry to
92 // the function. This field has no meaning for a variable sized element.
95 // The size of this object on the stack. 0 means a variable sized object,
96 // ~0ULL means a dead object.
99 // Alignment - The required alignment of this stack slot.
102 // isImmutable - If true, the value of the stack object is set before
103 // entering the function and is not modified inside the function. By
104 // default, fixed objects are immutable unless marked otherwise.
107 // isSpillSlot - If true, the stack object is used as spill slot. It
108 // cannot alias any other memory objects.
111 StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM,
113 : SPOffset(SP), Size(Sz), Alignment(Al), isImmutable(IM),
117 /// Objects - The list of stack objects allocated...
119 std::vector<StackObject> Objects;
121 /// NumFixedObjects - This contains the number of fixed objects contained on
122 /// the stack. Because fixed objects are stored at a negative index in the
123 /// Objects list, this is also the index to the 0th object in the list.
125 unsigned NumFixedObjects;
127 /// HasVarSizedObjects - This boolean keeps track of whether any variable
128 /// sized objects have been allocated yet.
130 bool HasVarSizedObjects;
132 /// FrameAddressTaken - This boolean keeps track of whether there is a call
133 /// to builtin \@llvm.frameaddress.
134 bool FrameAddressTaken;
136 /// StackSize - The prolog/epilog code inserter calculates the final stack
137 /// offsets for all of the fixed size objects, updating the Objects list
138 /// above. It then updates StackSize to contain the number of bytes that need
139 /// to be allocated on entry to the function.
143 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
144 /// have the actual offset from the stack/frame pointer. The exact usage of
145 /// this is target-dependent, but it is typically used to adjust between
146 /// SP-relative and FP-relative offsets. E.G., if objects are accessed via
147 /// SP then OffsetAdjustment is zero; if FP is used, OffsetAdjustment is set
148 /// to the distance between the initial SP and the value in FP. For many
149 /// targets, this value is only used when generating debug info (via
150 /// TargetRegisterInfo::getFrameIndexOffset); when generating code, the
151 /// corresponding adjustments are performed directly.
152 int OffsetAdjustment;
154 /// MaxAlignment - The prolog/epilog code inserter may process objects
155 /// that require greater alignment than the default alignment the target
156 /// provides. To handle this, MaxAlignment is set to the maximum alignment
157 /// needed by the objects on the current frame. If this is greater than the
158 /// native alignment maintained by the compiler, dynamic alignment code will
161 unsigned MaxAlignment;
163 /// HasCalls - Set to true if this function has any function calls. This is
164 /// only valid during and after prolog/epilog code insertion.
167 /// StackProtectorIdx - The frame index for the stack protector.
168 int StackProtectorIdx;
170 /// MaxCallFrameSize - This contains the size of the largest call frame if the
171 /// target uses frame setup/destroy pseudo instructions (as defined in the
172 /// TargetFrameInfo class). This information is important for frame pointer
173 /// elimination. If is only valid during and after prolog/epilog code
176 unsigned MaxCallFrameSize;
178 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
179 /// callee saved register saved in the frame. Beyond its use by the prolog/
180 /// epilog code inserter, this data used for debug info and exception
182 std::vector<CalleeSavedInfo> CSInfo;
184 /// CSIValid - Has CSInfo been set yet?
187 /// SpillObjects - A vector indicating which frame indices refer to
189 SmallVector<bool, 8> SpillObjects;
191 /// MMI - This field is set (via setMachineModuleInfo) by a module info
192 /// consumer (ex. DwarfWriter) to indicate that frame layout information
193 /// should be acquired. Typically, it's the responsibility of the target's
194 /// TargetRegisterInfo prologue/epilogue emitting code to inform
195 /// MachineModuleInfo of frame layouts.
196 MachineModuleInfo *MMI;
198 /// TargetFrameInfo - Target information about frame layout.
200 const TargetFrameInfo &TFI;
203 explicit MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) {
204 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
205 HasVarSizedObjects = false;
206 FrameAddressTaken = false;
208 StackProtectorIdx = -1;
209 MaxCallFrameSize = 0;
214 /// hasStackObjects - Return true if there are any stack objects in this
217 bool hasStackObjects() const { return !Objects.empty(); }
219 /// hasVarSizedObjects - This method may be called any time after instruction
220 /// selection is complete to determine if the stack frame for this function
221 /// contains any variable sized objects.
223 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
225 /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the
226 /// stack protector object.
228 int getStackProtectorIndex() const { return StackProtectorIdx; }
229 void setStackProtectorIndex(int I) { StackProtectorIdx = I; }
231 /// isFrameAddressTaken - This method may be called any time after instruction
232 /// selection is complete to determine if there is a call to
233 /// \@llvm.frameaddress in this function.
234 bool isFrameAddressTaken() const { return FrameAddressTaken; }
235 void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; }
237 /// getObjectIndexBegin - Return the minimum frame object index.
239 int getObjectIndexBegin() const { return -NumFixedObjects; }
241 /// getObjectIndexEnd - Return one past the maximum frame object index.
243 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }
245 /// getNumFixedObjects() - Return the number of fixed objects.
246 unsigned getNumFixedObjects() const { return NumFixedObjects; }
248 /// getNumObjects() - Return the number of objects.
250 unsigned getNumObjects() const { return Objects.size(); }
252 /// getObjectSize - Return the size of the specified object.
254 int64_t getObjectSize(int ObjectIdx) const {
255 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
256 "Invalid Object Idx!");
257 return Objects[ObjectIdx+NumFixedObjects].Size;
260 /// setObjectSize - Change the size of the specified stack object.
261 void setObjectSize(int ObjectIdx, int64_t Size) {
262 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
263 "Invalid Object Idx!");
264 Objects[ObjectIdx+NumFixedObjects].Size = Size;
267 /// getObjectAlignment - Return the alignment of the specified stack object.
268 unsigned getObjectAlignment(int ObjectIdx) const {
269 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
270 "Invalid Object Idx!");
271 return Objects[ObjectIdx+NumFixedObjects].Alignment;
274 /// setObjectAlignment - Change the alignment of the specified stack object.
275 void setObjectAlignment(int ObjectIdx, unsigned Align) {
276 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
277 "Invalid Object Idx!");
278 Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
281 /// getObjectOffset - Return the assigned stack offset of the specified object
282 /// from the incoming stack pointer.
284 int64_t getObjectOffset(int ObjectIdx) const {
285 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
286 "Invalid Object Idx!");
287 assert(!isDeadObjectIndex(ObjectIdx) &&
288 "Getting frame offset for a dead object?");
289 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
292 /// setObjectOffset - Set the stack frame offset of the specified object. The
293 /// offset is relative to the stack pointer on entry to the function.
295 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
296 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
297 "Invalid Object Idx!");
298 assert(!isDeadObjectIndex(ObjectIdx) &&
299 "Setting frame offset for a dead object?");
300 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
303 /// getStackSize - Return the number of bytes that must be allocated to hold
304 /// all of the fixed size frame objects. This is only valid after
305 /// Prolog/Epilog code insertion has finalized the stack frame layout.
307 uint64_t getStackSize() const { return StackSize; }
309 /// setStackSize - Set the size of the stack...
311 void setStackSize(uint64_t Size) { StackSize = Size; }
313 /// getOffsetAdjustment - Return the correction for frame offsets.
315 int getOffsetAdjustment() const { return OffsetAdjustment; }
317 /// setOffsetAdjustment - Set the correction for frame offsets.
319 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
321 /// getMaxAlignment - Return the alignment in bytes that this function must be
322 /// aligned to, which is greater than the default stack alignment provided by
325 unsigned getMaxAlignment() const { return MaxAlignment; }
327 /// setMaxAlignment - Set the preferred alignment.
329 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
331 /// hasCalls - Return true if the current function has no function calls.
332 /// This is only valid during or after prolog/epilog code emission.
334 bool hasCalls() const { return HasCalls; }
335 void setHasCalls(bool V) { HasCalls = V; }
337 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
338 /// allocated for an outgoing function call. This is only available if
339 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
340 /// then only during or after prolog/epilog code insertion.
342 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
343 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
345 /// CreateFixedObject - Create a new object at a fixed location on the stack.
346 /// All fixed objects should be created before other objects are created for
347 /// efficiency. By default, fixed objects are immutable. This returns an
348 /// index with a negative value.
350 int CreateFixedObject(uint64_t Size, int64_t SPOffset,
351 bool Immutable, bool isSS);
354 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
355 /// fixed stack object.
356 bool isFixedObjectIndex(int ObjectIdx) const {
357 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
360 /// isImmutableObjectIndex - Returns true if the specified index corresponds
361 /// to an immutable object.
362 bool isImmutableObjectIndex(int ObjectIdx) const {
363 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
364 "Invalid Object Idx!");
365 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
368 /// isSpillSlotObjectIndex - Returns true if the specified index corresponds
369 /// to a spill slot..
370 bool isSpillSlotObjectIndex(int ObjectIdx) const {
371 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
372 "Invalid Object Idx!");
373 return Objects[ObjectIdx+NumFixedObjects].isSpillSlot;;
376 /// isDeadObjectIndex - Returns true if the specified index corresponds to
378 bool isDeadObjectIndex(int ObjectIdx) const {
379 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
380 "Invalid Object Idx!");
381 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
384 /// CreateStackObject - Create a new statically sized stack object,
385 /// returning a nonnegative identifier to represent it.
387 int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS) {
388 assert(Size != 0 && "Cannot allocate zero size stack objects!");
389 Objects.push_back(StackObject(Size, Alignment, 0, false, isSS));
390 int Index = (int)Objects.size()-NumFixedObjects-1;
391 assert(Index >= 0 && "Bad frame index!");
392 if (SpillObjects.size() <= static_cast<unsigned>(Index))
393 SpillObjects.resize(Index+1);
394 SpillObjects[Index] = false;
398 /// CreateSpillStackObject - Create a new statically sized stack
399 /// object that represents a spill slot, returning a nonnegative
400 /// identifier to represent it.
402 int CreateSpillStackObject(uint64_t Size, unsigned Alignment) {
403 CreateStackObject(Size, Alignment, true);
404 int Index = (int)Objects.size()-NumFixedObjects-1;
405 if (SpillObjects.size() <= static_cast<unsigned>(Index))
406 SpillObjects.resize(Index+1);
407 SpillObjects[Index] = true;
411 /// RemoveStackObject - Remove or mark dead a statically sized stack object.
413 void RemoveStackObject(int ObjectIdx) {
415 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
418 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
419 /// variable sized object has been created. This must be created whenever a
420 /// variable sized object is created, whether or not the index returned is
423 int CreateVariableSizedObject() {
424 HasVarSizedObjects = true;
425 Objects.push_back(StackObject(0, 1, 0, false, false));
426 return (int)Objects.size()-NumFixedObjects-1;
429 /// isSpillObject - Return whether the index refers to a spill slot.
431 bool isSpillObject(int Index) const {
432 // Negative indices can't be spill slots.
433 if (Index < 0) return false;
434 assert(static_cast<unsigned>(Index) < SpillObjects.size() &&
435 "Invalid frame index!");
436 return SpillObjects[Index];
439 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
440 /// current function.
441 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
445 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
446 /// callee saved information.
447 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
451 /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet?
452 bool isCalleeSavedInfoValid() const { return CSIValid; }
454 void setCalleeSavedInfoValid(bool v) { CSIValid = v; }
456 /// getPristineRegs - Return a set of physical registers that are pristine on
457 /// entry to the MBB.
459 /// Pristine registers hold a value that is useless to the current function,
460 /// but that must be preserved - they are callee saved registers that have not
463 /// Before the PrologueEpilogueInserter has placed the CSR spill code, this
464 /// method always returns an empty set.
465 BitVector getPristineRegs(const MachineBasicBlock *MBB) const;
467 /// getMachineModuleInfo - Used by a prologue/epilogue
468 /// emitter (TargetRegisterInfo) to provide frame layout information.
469 MachineModuleInfo *getMachineModuleInfo() const { return MMI; }
471 /// setMachineModuleInfo - Used by a meta info consumer (DwarfWriter) to
472 /// indicate that frame layout information should be gathered.
473 void setMachineModuleInfo(MachineModuleInfo *mmi) { MMI = mmi; }
475 /// print - Used by the MachineFunction printer to print information about
476 /// stack objects. Implemented in MachineFunction.cpp
478 void print(const MachineFunction &MF, raw_ostream &OS) const;
480 /// dump - Print the function to stderr.
481 void dump(const MachineFunction &MF) const;
484 } // End llvm namespace